The factors of knot strength and debonding techniques are reviewed. The aesthetic advantage of ceramic brackets is that it is the main reason that is favored by orthodontic patients, and its bonding strength and debonding technology have always been the focus of clinicians. Proper handling can avoid disadvantages. Improper handling can cause problems for patients. Unrecoverable loss. This article reviews the content and research progress of this aspect. 1 Types of ceramic brackets The main material for making ceramic brackets is alumina. According to different manufacturing methods, it is divided into single crystal aluminum and polycrystalline aluminum brackets. The appearance of single crystal aluminum brackets is better, while polycrystalline aluminum trays The trough is relatively simple to make, and the polycrystalline aluminum bracket is used in clinical practice. According to the different retention methods, it can be divided into mechanical retention type, chemical retention type and mixed retention type ceramic bracket. According to the groove size, it is divided into 0.046cm (0.018") and 0.056cm (0.022") brackets. From the technical characteristics, it is divided into standard square wire bow ceramic bracket, straight wire bow ceramic bracket and Begg ceramic bracket. According to the material characteristics of the groove, it is divided into ordinary ceramic brackets and ceramic brackets with metal grooves. 2 Ceramic bracket bonding retention principle 2.1 Mechanically-retained ceramic bracket Mechanically-retained ceramic bracket is made by using the groove, undercut or crypt on the bracket bottom plate to mechanically lock with the adhesive. Compared with the metal bracket, the bottom plate has less anchoring structure than the metal bracket, and stress concentration is easy to occur when the force is applied, so that the binder is broken, so the bonding strength is not as good as the metal bracket which is also locked by the mechanical lock; The metal bottom plate type ceramic bracket is born, that is, the metal bottom plate is well retained, and the enamel is not easily damaged when the bracket is removed. 2.2 Chemically Retaining Ceramic Brackets These brackets are provided with a glass component, and the bottom plate is smooth. The silane coupling agent is applied to the surface of the substrate before bonding, and then bonded with an adhesive. The silane coupling agent is a bifunctional group, one end is an inorganic reactive group, and can be firmly attached to the inorganic porcelain surface, and the other end is an organic reactive group, which can be copolymerized with the binder resin. The stress is distributed throughout the bonding interface, and there is no local stress concentration. Therefore, the bonding strength is higher than that of the mechanically-retained ceramic bracket and the metal bracket, but the enamel is easily damaged when the bracket is removed by the clamp. In addition, polycarbonate or epoxy resin components are added to the ceramic bracket base, which can be chemically bonded to the binder, and the bonding strength is lower than that of the silane. When the tongs are removed, the enamel is not easily damaged. 2.3 Mixed Retention Ceramic Bracket refers to a bracket that combines the above two retention principles. For example, some ceramic brackets mainly rely on chemical bonding and retention, and the bottom plate also has some structures such as micro-crypts, that is, the mechanical retention principle is also combined. 3 Factors affecting bond strength 3.1 Bracket type It is considered that the bond strength of single crystal aluminum bracket is larger than that of polycrystalline aluminum bracket; the bond strength of chemically retained ceramic bracket is larger than that of mechanically retained ceramic bracket. 3.2 Binder type The binder is divided into resin binder, glass ion binder, etc. according to the material, and is divided into photocuring and chemical curing binder according to the curing method. Hitmi et al. reported a good bonding effect with a glass ion containing a resin component; Haydar et al. showed that photocurable glass ions are suitable binders for ceramic brackets. In addition, fluorine-containing binders are also a hot spot of research. 3.3 Dry junction method It is generally believed that the bond strength of the direct bond method is higher than that of the indirect bond method; some people also prefabricate the bond coat on the bracket bottom plate, and research shows that it does not affect the bond strength of the bracket. 3.4 Acid etching technology Currently, the acid etching agent is 37% phosphoric acid, and the optimum etching time is 30s. In this range, the bonding strength is not statistically different due to time, and the time is too long or too short will affect the bonding. Strength, need to prolong the acid etching time for dental fluorosis. Some scholars have also studied the use of crystal growth technology instead of acid etching technology, but it is still in the experimental stage. 3.5 Enamel conditions The enamel conditions of dental fluorosis or bleached teeth affect the bond strength. Studies have shown that hydrogen peroxide bleaching the teeth reduces the bond strength of the ceramic brackets. 3.6 One of the main application groups of artificial restoration ceramic brackets is adult patients, one of which is characterized by an intraoral restoration. With the popularity of porcelain teeth, the bonding between ceramic brackets and porcelain teeth has always been a research hotspot. Kocadereli et al. suggested that the porcelain tooth surface should be sandblasted or acid etched first, then treated with silane, and the bond strength is best; Chung et al. It shows that the blasting of porcelain teeth or alloy surface can achieve the same bond strength as enamel acid etching; while ZachriSSn believes that the etched sand after porcelain blasting can provide the bonding strength suitable for clinical needs. The application of silane is Selective. Bonding with amalgam can be carried out by alloy surface blasting-primer treatment-adhesive bonding. When bonding with the resin restoration, the surface may be roughened with sandpaper or the like, and then bonded with a resin binder. The bond with the gold alloy is mainly by sandblasting the alloy and then bonding with a binder. However, the restoration of the original artificial prosthesis after the removal of the bracket is still an urgent problem to be solved. In addition to the above objective factors, subjective factors such as the skill level of the operator and the patient cooperation during bonding may also affect the bond strength. The research on the bond strength of ceramic brackets is clinical experiment, and the other is laboratory design, and the research conclusions of the two are not always coordinated, which is mainly caused by the complexity of the oral environment, such as oral cavity. The temperature, humidity, plaque environment and other conditions of the laboratory can not be copied, resulting in deviations between the experimental results and the real situation; and clinical trials have more interference factors (such as patient compliance), so that some clinical research results and real conditions also have Out of person. Therefore, a comprehensive analysis of the results of different studies is required to have a comprehensive understanding. 4 Debonding Technology 4.1 Clamp Removal Method The pliers removal method uses pliers designed for ceramic brackets. Some companies also have special pliers and corresponding methods for the company's products. The stress required for different de-slot devices is also different. . The method is broken by the bracket-binder interface, or the adhesive is broken due to stress, so that the bracket is separated from the tooth surface. When the mechanical retention bracket is removed, more than the binder-to-slot interface is broken; when the chemical retention bracket is removed, the binder-enamel interface is often broken, and the enamel is easily damaged. The pliers removal method is simple and easy, but it also has disadvantages: 1 may damage the enamel. Removal of single-crystal aluminum brackets and chemically-retained brackets is relatively harmful to enamel; if the teeth are not in good condition (such as enamel cracks and dead fangs), enamel is easily damaged when the bracket is removed. The metal backplane design, with a polycarbonate or epoxy layer on the bottom plate, reduces the risk of enamel damage when the bracket is removed. 2 may cause the bracket fragment to be sucked. The ceramic bracket is brittle and can be accidentally broken when removed. 3 The removal of the remaining ceramic chips is more time consuming, and the large amount of ceramic dust generated during the grinding may also irritate the skin or eyes of the patient or the doctor. If the cooling measures are improper, the heat generated during the grinding may damage the pulp. 4 exertion when removing will make some patients feel pain. 4.2 Electric gun method The electric gun method is heated by a special electric gun. When sufficient heat penetrates the bracket-binder interface, it is supplemented with appropriate stress, and the bracket will be separated from the tooth surface. Regarding the question of whether electrothermal high temperature affects the vitality of the pulp, studies have shown that under normal circumstances, the operation time of the electrothermal method to the bracket is short, and the temperature does not exceed the threshold of the pulp tissue damage, unless repeated heating and insufficient cooling Damage the pulp. The main disadvantage of this method is that the head of the electric gun is large, especially in the premolar area, and the falling of the heat bracket to the mouth can cause discomfort to the patient. 4.3 Peppermint Oil Preparation Method The peppermint oil preparation is applied around the ceramic bracket to remove the bracket by promoting the separation of the binder-enamel interface. This method is simple and does not damage the teeth, but the research of 11 shows that it is softening and sticking. There is still no convincing evidence for the effectiveness of the seal. 4.4 Ultrasonic to dry knot technology advantages: reduce enamel damage; reduce the possibility of bracket breakage; can simultaneously remove residual adhesive on the tooth surface. Disadvantages: time-consuming; removal of hard ceramic brackets can severely deplete the ultrasonic probe; improper cooling during operation can damage the pulp. 4.5 Laser method The laser bracket is used to remove the ceramic bracket. The laser irradiation can reduce the stress of the bracket by the softening of the bonding matrix, which is beneficial to reduce enamel damage, avoid bracket breakage and reduce patient discomfort. However, this method requires laser equipment, and some people have doubts about the possible damage caused by laser heat to the pulp. The method is still in the research stage. In summary, the most widely used method is the clamp removal method. For the enamel damage problem, there are ceramic brackets for metal or other component bottom plates that are suitable for removal with pliers. The bond strength can meet the clinical needs; the gun head used in the electric gun method Large, ultrasonic method is costly, laser method requires special equipment, and all three methods have heat production, special attention should be paid to the problem of pulp damage; chemical method is easy to operate, but there is no breakthrough in material science. At present, the types and quantities of ceramic brackets used in China are limited. The research on the removal method has not been reported. The clinical use of clamp removal method is mainly used for mechanically-retained ceramic brackets. However, you should be very cautious about chemically-retained ceramic brackets. 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Bonding and removal of ceramic brackets